Sag, static vs rider

Discussion in 'Mechanics Garage' started by Camp, Feb 5, 2020.

  1. Camp

    Camp New Member

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    In taking measurements is it safe to assume that when rider on sag is set correctly if the static sag is zero (topping out) the spting rate is too high (stiff)?

    Conversely if the static sag is within specs and the rider height is too low spring rate is too low?

    Seems to me in either case dampening will be hard to get right but especially in the first when it's topping out.

    Any thoughts appreciated.
     
  2. Captain 80s

    Captain 80s Member

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    Pretty sure it's the opposite in your first example (too light of spring) which I know sounds counter-intuitive. It means you had to dial in so much preload to get the rider sag right, unladen there is no static sag. You need a heavier spring with less preload to get both in the sweet spot.

    I think your second example is just the same scenario with the preload backed off on too light of a spring. If you increase the preload to get rider sag correct, you're gonna lose the static sag.

    But I haven't had my evening beer in the shop yet, so my head might not be right.
     
    Last edited: Feb 5, 2020
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  3. NorcalBoy

    NorcalBoy Member

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    1.) Yes
    2.) Yes

    I have always relied on the spring, with no preload, and adjusted the spring rate to achieve that. It can take a little work to get it there, but at that point you don't ever have to screw around with it. You know with this spring rate, it always going to be in the correct range and you never have to adjust the preload. I prefer mine to be towards the stiffer end of the range, with no preload, and the lightest oil I can use, and just varying oil height to control the bottoming. But that's just me. Cranking on the preload just screws up the geometry.

    My standard rule of thumb (stolen from Ohlins) is:
    Free Sag (What you refer to as static sag):

    Rear - 5-15 mm
    Front - 20-30 mm

    Ride Height (What you refer to as rider sag)

    Rear - 25-35 mm
    Front - 30-40 mm

    If you have stock suspension, you aren't going to get much adjustment, other than ride height (preload) and rebound.
     
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